Polymeric multilayer film

ABSTRACT

Polymeric multilayer film comprising at least two adjacent layers each exhibiting a random network of strands and connective regions. The polymeric multilayer films are useful, for example, for tape and graphic articles.

CROSS REFERENCE TO RELATED APPLICATION

This application is a national stage filing under 35 U.S.C. 371 ofPCT/US2017/064400, filed Dec. 4, 2017, which claims the benefit of U.S.Provisional Application No. 62/432361, filed Dec. 9, 2016, thedisclosure of which is incorporated by reference in its/their entiretyherein.

BACKGROUND

There is a desire to make polymeric films and film composites withstructures and/or textures to provide additional functionality. Suchfunctionality may include optical effects, and/or increased liquidabsorption or solid retention due to the increased surface area of atexture surface vs. a smooth surface.

Textures or structures can be added to polymeric films, for example, viacasting molten polymer onto a patterned chill roll. This requires theuse of a specific patterned roll for each desired texture or structuredfilm. Alternatively, a non-patterned polymeric film can be embossedafter the film-making process by reheating at least a portion of thefilm surface and passing between a high-pressure nip with at least oneof the rollers having the reverse of the desired pattern. This techniquerequires an additional process step and requires the manufacture and useof a patterned roll for each desired final texture or structure.

Textured films can also be produced coating or laminating a polymericlayer onto a nonwoven web. The nonwoven layer provides the desiredtexture or structure while the film layer provides other functionalitysuch as a barrier or decorative layer. This process requires multipleprocess steps to produce the desired end product—producing a non-wovenweb and at least a second step to provide the lamination or coating ofthe polymer layer onto the nonwoven.

There remains a need to produce a structured and/or textured polymericfilm or film composite that can be produced without the need for uniquepatterned rolls or without the need for a secondary process to producethe texture or structure.

SUMMARY

The present disclosure describes a polymeric multilayer film comprisingat least two adjacent polymeric layers, each exhibiting a random networkof strands (in some embodiments, elongated strands) and connectiveregions (the random network has a first optical density and theconnective regions has a second optical density, wherein the firstoptical density is greater than the second optical density; in someembodiments, there are openings in at least some of the connectiveregions, whereas in some embodiments there are no openings (i.e., nothrough holes) in the layer). In some embodiments, at least 3, 4, 5, 6,or even at least 7 polymeric layers, each exhibit a random network ofstrands and connective regions. In some embodiments, all the layers, orsome of the layers are adjacent another layer exhibit a random networkof strands and connective regions.

Embodiments of polymeric multilayer films described herein are useful,for example, for tape and graphic articles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view schematic of an exemplary polymeric multilayer filmdescribed herein.

FIG. 1A is a side view of the exemplary polymeric multilayer film shownin FIG. 1.

FIG. 2 is a top view schematic of another exemplary random network ofstrands and connective regions.

FIG. 3 is an exemplary apparatus for making polymeric multilayer filmdescribed herein.

FIG. 3A is an exemplary annular die used in the apparatus shown in FIG.3.

FIGS. 4 and 4A are optical images of Example 1 polymeric multilayerfilm.

FIGS. 5 and 5A are optical images of Example 2 polymeric multilayerfilm.

FIGS. 6 and 6A are optical images of Example 3 polymeric multilayerfilm.

DETAILED DESCRIPTION

The present disclosure describes a polymeric multilayer film comprisingat least two adjacent polymeric layers, each exhibiting a random networkof strands (in some embodiments, elongated strands) and connectiveregions (the random network has a first optical density and theconnective regions has a second optical density, wherein the firstoptical density is greater than the second optical density; in someembodiments, there are openings in at least some of the connectiveregions, whereas in some embodiments there are no openings (i.e., nothrough holes) in the layer). In some embodiments, at least 3, 4, 5, 6,or even at least 7 polymeric layers, each exhibiting a random network ofstrands and connective regions. In some embodiments, all the layers, orsome of the layers are adjacent another layer exhibiting a randomnetwork of strands and connective regions. In some embodiments, at leastone of the first or second (in some embodiments each of the first andsecond) major surfaces of a polymeric multilayer film exhibits a randomnetwork of strands and connective regions.

Referring to FIGS. 1 and 1A, exemplary polymeric multilayer film 100 hasfirst and second adjacent layers 101, 102, respectively, each exhibitingrandom network of strands 103 and connective regions 104. As shown,first and second adjacent layers 101, 102 as disposed between (optional)continuous layers 105 and 106, respectively. In order to see layer 101,continuous layer 105 is not shown in FIG. 1.

Referring to FIG. 2, another example of random network of strands 203and connective regions 204 is shown.

In some embodiments, a layer exhibiting a random network of strands andconnective regions independently comprises at least one of apolyolefinic material (e.g., polypropylene and/or polyethylene),modified polyolefinic material, polyvinyl chloride, polycarbonate,polystyrene, polyester (including co-polyester), polylactide,polyvinylidene fluoride, (meth)acrylic (e.g., polymethyl methacrylate),urethane, acrylic urethane, ethylene vinyl acetate copolymer,acrylate-modified ethylene vinyl acetate polymer, ethylene acrylic acidcopolymers, nylon, engineering polymer (e.g., a polyketone and/orpolymethylpentane), or elastomer (e.g., natural rubber; syntheticrubber; styrene block copolymer containing isoprene, butadiene, orethylene (butylene) blocks; metallocene-catalyzed polyolefin,polyurethanes; or polydiorganosiloxane).

In some embodiments, a layer exhibiting a random network of strands andconnective regions has an open porosity of at least 1 (in someembodiments, at least 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65,70, 75, or even at least 80; in some embodiments, in a range from 1 to80) percent.

In general, polymeric multilayer film comprising at least two adjacentlayers, each exhibiting a random network of strands and connectiveregions described herein, can be made by overfoaming a layer in a blownfilm process that uses an annular die to form a molten tube of filmoriented radially via air pressure in a “bubble,” and also pulledlengthwise in the molten area to thin the film to the final desiredthickness. For example, referring to FIG. 3, apparatus for makingpolymeric multilayer film comprising at least two adjacent layers, eachexhibiting a random network of strands and connective regions describedherein 300 includes hopper 304, extruder 306, annular die 308, air ring310, collapsing frame 314, rollers 316A, 316B that form nip 317,slitting station 323 and idler rolls 318, 319. Referring to FIG. 3A,further details of nine-layer annular die 308 are shown, includingstacked die plates, with each individual die plate stack layer havingmachined polymer flow channels 309A, 309B, 309C, 309D, 309E, 309F, 309G,309H, 309I. During the film making process the molten polymer passesthrough the flow channels 309A, 309B, 309C, 309D, 309E, 309F, 309G,309H, 309I and contacts central die cylinder 310 and then flows upwardcombining with other layers and exits annular die opening 311 to formmultilayered film tube 312. The number of layers in the polymericmultilayer film can be adjusted by the number of stacking die plates inthe annular die.

In operation, resin 302 (typically in the form of pellets) and otheradditives are added to hopper 304. Molten or otherwise flowable resinexits extruder 306 into annular die 308. Air ring 310 provides uniformair flow over the molten polymer bubble which stabilizes and aids incooling of the polymer bubble forming circular film bubble 312 into acollapsed film tube 320 by passing through nip 317 formed by contactingnip rolls 316A and 316B. The collapsed film tube traverses idler rolls318 and passes through slitting station 323 resulting in the formationof two flat films 320A and 320B that are passed over additional idlerroll 319. Films 320A and 320B are then wound into individual rolls 321Aand 321B, respectively. A layer(s) of the polymeric multilayer film canbe foamed or overfoamed, for example, by introducing a gas into themolten polymer inside the extruder. The gas is readily absorbed into thepolymer under the heat and pressure of the extrusion process. When themolten polymer exits the extrusion die, the absorbed, pressurized gasrapidly expands and forms voids. The proper process conditions can beadjusted so that when the polymer solidifies, the void structure is“locked in” resulting in a foam structure in the polymeric film.

Foaming of a layer(s) can be facilitated, for example, by including orinjecting a foaming agent in the resin for that layer(s). Foaming agentsare known in the art and include injecting gases, (e.g., nitrogen orcarbon dioxide) into the molten polymer. Foaming agents are known in theart, and include a blend of alkaline earth metal carbonates and alkalinemetal acid salts that are described in U.S. Pat. No. 8,563,621(Lapierre), the disclosure of which is incorporated herein by reference.Exemplary commercially available blowing agents include those under thetrade designation “ECOCELL H” from Polyfil Corp., Rockaway, N.J. Otherexemplary chemical blowing agents for polymers are well known in the artand include hydrazine, hydrazide, and azodicarbonamide materials (e.g.,4,4′-oxybis (benzenesulfonyl hydrazide) (OBSH) (available, for example,in a masterbatch form under the trade designation “CELOGEN OT” fromChemPoint, Bellevue, Wash.). Another exemplary chemical blowing agent isan endothermic foaming agent, available as a masterbatch under the tradedesignation “FCX111263” from RTP Company, Winona, Minn.

In some embodiments, the forming agent is added to the resins that isfed into the extruder. The foaming agent and other processing conditionsare selected or adjusted to provide a desired or acceptable polymericmultilayer film comprising a layer(s) exhibiting a random network ofstrands and connective region.

In some embodiments, at least one layer of a polymeric multilayer filmdescribed herein comprises an ultraviolet (UV) absorber. A UV absorbinglayer (e.g., a UV protective layer) can aid in protecting other layersor substrates from UV-light caused damage/degradation over time byabsorbing UV-light (in some embodiments, any UV-light).

In some embodiments, the UV absorbers are red shifted UV absorbers(RUVA) that absorb at least 70% (in some embodiments, at least 80%, oreven at least 90%) of the UV light in the wavelength region from 180 nmto 400 nm. Typically, it is desirable that the RUVA be highly soluble inpolymers, highly absorptive, photo-permanent, and thermally stable in atleast the temperature range from 200° C. to 300° C. for extrusionprocess to form the protective layer. In some embodiments, a RUVA iscopolymerizable with monomers to form a protective coating layer by atleast one of free radical initiator curing, UV curing, gamma ray curing,e-beam curing, or thermal curing processes. Exemplary UVAs are UVAoligomers as described, for example, in PCT Pub. Nos. WO 2014/10055A1(Olson et. al.), WO 2014/100580A1 (Olson et. al.), WO 2015/200655 (Olsonet. al.), WO 2015/200669 (Olson et. al.), and WO 2015/200657 (Olson et.al.), the disclosure of which are incorporated herein by reference.

RUVAs typically have enhanced spectral coverage in the long-wave UVregion (i.e., 300 nm to 400 nm), enabling them to block the highwavelength UV light that can cause yellowing in most polymers. TypicalUV protective layers have thicknesses in a range from about 13micrometers to 380 micrometers with a RUVA loading level in a range fromabout 2-10% by weight. Exemplary RUVAs include benzotriazole compound,5-trifluoromethyl-2-(2-hydroxy-3-alpha-cumyl-5-tert-octylphenyl)-2H-benzotriazole(available under the trade designation “CGL-0139” from BASF Corporation,Florham, N.J.), benzotriazoles (e.g.,2-(2-hydroxy-3,5-di-alpha-cumylphehyl)-2H-benzotriazole,5-chloro-2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-2H-benzotriazole,5-chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole,2-(2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole,2-(2-hydroxy-3-alpha-cumyl-5-tert-octylphenyl)-2H-benzotriazole,2-(3-tert-butyl-2-hydroxy-5-methylphenyl)-5-chloro-2H-benzotriazole),and 2(-4,6-diphenyl-1-3,5-triazin-2-yl)-5-hexyloxy-phenol. Additionalcommercially available RUVAs include those available from BASFCorporation under the trade designations “TINUVIN 1577,” “TINUVIN 1600,”and “TINUVIN 777.” Other exemplary UV absorbers are available, forexample, in a polymethylmethacrylate (PMMA) UVA masterbatch from SukanoPolymers Corporation, Duncan, S.C., under the trade designations“TA11-10 MB03.”

In some embodiments, at least one layer of a polymeric multilayer filmdescribed herein comprises a hindered amine light stabilizer (HALS).Exemplary HALS include those available from BASF Corporation under thetrade designations “CHIMASSORB 944” and “TINUVIN 123.” Another exemplaryHALS is available, for example, from BASF Corp., under the tradedesignation “TINUVIN 944.”

In some embodiments, at least one layer of a polymeric multilayer filmdescribed herein comprises an antioxidant. Exemplary antioxidantsinclude those available under the trade designations “IRGANOX 1010” and“ULTRANOX 626” from BASF Corporation.

In some embodiments, at least one layer of a polymeric multilayer filmdescribed herein comprises an antioxidant. Antioxidants can reduce orprevent degradation of the color development, and the physical andmechanical properties of the polymeric multilayer film. Exemplaryantioxidant materials include those commercially available, for example,under the trade designations “CYANOX 1790” and “CYANOX 2777” from CytecSolvay Group, Woodland Park, N.J.

In some embodiments, at least one layer of a polymeric multilayer filmdescribed herein comprises a hydrophilic material. Hydrophilic additivescan increase absorption of aqueous liquids. This may be useful, forexample, for cleaning products to absorb spills and aqueous cleaningagents, and medical applications to absorb body fluids. Exemplaryhydrophilic materials include an anionic surfactant, available, forexample, under the trade designation “JDOSS 50P” from JLK Industries,Coopersburg, Pa., or a non-ionic surfactant (PEG-5 Cocamide), available,for example, under the trade designation “HETOXAMIDE C4” from Global 7Industries, Franklin, N.J.

In some embodiments, at least one layer of a polymeric multilayer filmdescribed herein comprises at least one antistatic material. Antistaticmaterials can, for example, reduce dust and dirt attraction to finishedproducts, reduce sparks through discharges, reduce ignition of flammableliquid and gas, reduce damage to electronic microcircuits, and reducejamming of transport equipment. Exemplary antistatic materials includethose available under the trade designations “CTASTAT 609” and “CYASTATSN” from Cytec Solvay Group, Woodland Park, N.J.

In some embodiments, at least one layer of a polymeric multilayer filmdescribed herein comprises a release agent. Exemplary release agentsinclude at least one of an alkyl dimethicone, a polyvinyl octadecylcarbamate, or an ethylene bis-stearamide. Alkyl dimethicones, aredescribed, for example, in U.S. Pat. No. 9,187,678 (Boardman et al.). Apolyvinyl octadecyl carbamate is commercially available, for example,under the trade designation “ESCOAT P-77” (a polyvinyl octadecylcarbamate in a linear, low density carrier resin) from Mayzo, Inc.,Suwanee, Ga. An ethylene bis-stearamide is available, for example, underthe trade designation “AMPACET 100666” from Ampacet Corporation,Tarrytown, N.Y. Pressure sensitive adhesive tapes, or adhesive tapes,are often provided in roll form, wherein the tape construction includesa backing, an adhesive layer on one major side of the backing, and arelease layer on the other major side of the backing. The release layerallows the tape to be unwound from the roll at a controlled level. Otherarticles having release characteristics are employed in a variety ofapplications. Any adhesive coated article, including tapes, die-cutadhesive articles, and labels, require, as a matter of practicality, arelease coating or a separate release liner. The release coating orliner provides a surface to which the article does not permanentlyadhere.

In some embodiments, at least one layer of a polymeric multilayer filmdescribed herein comprises at least one of a slip additive or blockingagent. Slip additives can modify the surface properties of a film,lowering the friction between film layers and other surfaces. To beeffective, the slip needs to migrate out of the polymer to the surfaceand therefore, it needs have a degree of incompatibility with thepolymer.

Exemplary slip additives include fatty acid amides such as erucamide oroleamide. During processing, slip additives solubilize in the amorphousmelt, but as the polymer cools and crystalizes, the fatty acid amide is“squeezed” out, forming a lubricating layer at the polymer surface. Theaddition of a slip additive can reduce or prevent film sticking andpulling, helping to increase throughput. Exemplary slip additives arecommercially available, for example, under the trade designations“AMPACET 100497” (a masterbatch containing 1% erucamide, in low densitypolyethylene carrier resin); and “#10358” (a masterbatch of 5% oleamide,in a polyethylene carrier) from Ampacet Corporation, Tarrytown, N.Y.

A blocking agent can reduce or prevent blocking of layers. Polyolefinand other plastic films have a tendency to adhere together, often makingit difficult to separate layers. This adhesion between film layers,called blocking, is an inherent property of some polymers. Antiblockingadditives can be added to the film to minimize this adhesion and lowerthe blocking force between layers. Once compounded into a plastic, theseadditives create a microrough surface, which reduces the adhesionbetween film layers and lowers the blocking tendency. Exemplaryantiblock agents are typically inorganic materials such as diatomaceousearth, talc, calcium carbonate, clay, mica and ceramic spheres. Anexemplary antiblock agent is commercially available, for example, underthe trade designations “ABC5000” from Polyfil Corporation, Rockaway,N.J.; and “AMPACET 102077” from Ampacet Corp.

In some embodiments, at least one layer of a polymeric multilayer filmdescribed herein comprises an abrasion resistant material. Abrasionresistant materials may be added to reduce scratching, marring andabrasion of the finished product. An exemplary abrasion resistantadditive is commercially available, for example, under the tradedesignation “MB25-381” (a masterbatch containing a siloxane polymer)from Dow Corning, Auburn Mich.

In some embodiments, at least one layer of a polymeric multilayer filmdescribed herein comprises at least one of a dye or pigment (e.g.,imparting a color such as white, yellow, green, blue, red, orange,brown, black, etc.). Exemplary dyes include those commerciallyavailable, for example, under the trade designation “CLARIANT REMAFINPE63421213-ZN” (a green dye masterbatch) from Clariant International AG,Muttenz, Switzerland. Exemplary pigments include titanium dioxide, zincoxide, and zirconium dioxide. An exemplary pigment, commerciallyavailable masterbatch of titanium dioxide pigment in a polyolefincarrier, under the trade designation “#11937” from Standridge ColorCorporation, Social Circle, Ga.

In some embodiments, at least one layer of a polymeric multilayer filmdescribed herein comprises at least one of an ink or paint receptivematerial. Ink receptive materials can be desirable for adding aninformational or decorative element to a film to improve thefunctionality or aesthetics of the film. Exemplary receptive materialsinclude, for example, ethylene/vinyl acetate/carbon monoxide terpolymer,as described, for example, in U.S. Pat. No. 6,316,120 (Emslander), thedisclosure of which is incorporated herein by reference.

In some embodiments, at least one layer of a polymeric multilayer filmdescribed herein comprises metallic (e.g., aluminum, bronze, stainlesssteel, zinc, iron, tin, silver, gold, and/or titanium) particles.Metallic particles can provide unique decorative aspects, such assparkle or pearlescence to films. An exemplary metallic particleadditive is commercially available, for example, under the tradedesignation “PELLEX A240-50” (a metallic glitter masterbatch) from TheCary Company, Addison, Ill.

In some embodiments, at least one layer exhibiting a random network ofstrands and connective regions is separable from the remaining polymericmultilayer film.

In some embodiments, at least one layer of a polymeric film describedherein, including a layer exhibiting a random network of strands andconnective regions, comprises an adhesive (including pressure sensitiveadhesives).

In some embodiments, at least one layer of a polymeric film describedherein, including a layer exhibiting a random network of strands andconnective regions, is essentially free of pressure sensitive adhesive.In some embodiments, the layer exhibiting a random network of strandsand connective regions comprises a pressure sensitive adhesive.Exemplary pressure sensitive adhesives include those available, forexample, under the trade designations “OCA8171” and “OCA8172” from 3MCompany, St. Paul, Minn. Extrudable pressure sensitive adhesives arecommercially available, for example, under the trade designations“LIR-290,” “LA2330,” “LA2250,” “LA2140E,” and “LA1114” from Kuraray,Osaka, Japan; and “ESCORE” from Exxon Mobil, Irving, Tex. The tackinessof pressure sensitive adhesives can be adjusted, for example, withtackifiers.

Other exemplary adhesives include isobutylene/isoprene copolymersavailable, for example, under the trade designations “EXXON BUTYL 065,”“EXXON BUTYL 068,” and “EXXON BUTYL 268” (believed to have unsaturationin the range of about 1.05 to about 2.30 mole percent) from Exxon MobilCorp.; “BK-1675N” (believed to have unsaturation of about 1.7 molepercent) from United Chemical Products, Velizy-Villacoublay, France;“LANXESS BUTYL 301” (believed to have an unsaturation of about 1.85 molepercent), “LANXESS BUTYL 101-3” (believed to have unsaturation of about1.75 mole percent), and “LANXESS BUTYL 402” (believed to haveunsaturation of about 2.25 mole percent) from Lanxess, Sarnia, Ontario,Canada; and “SIBSTAR” (available as both diblocks and triblocks with thestyrene content believed to vary from about 15 to about 30 mole percent,based on the mole percent of the copolymer) from Kaneka, Osaka, Japan.Exemplary polyisobutylene resins are commercially available, forexample, from under the trade designations “VISTANEX” from ExxonChemical Co., Irving, Tex.; “HYCAR” from Goodrich Corp., Charlotte,N.C.; and “JSR BUTYL” from Japan Butyl Co., Ltd., Kanto, Japan.

In general, suitable polyisobutylenes may have a wide variety ofmolecular weights and a wide variety of viscosities. In someembodiments, the polyisobutylene has a weight average molecular weight(as measured by Gel Permeation Chromatography using polystyrenestandards) of at least about 300,000 (in some embodiments, at leastabout 400,000, or even at least 500,000 or more) grams per mole. In someembodiments, the polyisobutylene has a weight average molecular weightof less than 300,000 (in some embodiments, up to 280,000, 275,000,270,000, 260,000, 250,000, 240,000, 230,000, 220,000, 210,000, or up to200,000) grams per mole. In some embodiments, when defined by theviscosity as measured by intrinsic viscosity at 20° C. in diisobutylene,the polyisobutylene has a viscosity average molecular weight in a rangefrom 100,000 to 10,000,000 (in some embodiments, 500,000 to 5,000,000)grams per mole. Polyisobutylenes of many different molecular weights andviscosities are commercially available. In some embodiments, themolecular weight of the polyisobutylene changes during the process ofmaking a pressure sensitive adhesive.

In some embodiments, pressure sensitive adhesives that comprisepolyisobutylene further comprises a hydrogenated hydrocarbon tackifier(in some embodiments, a poly(cyclic olefin)). In some embodiments, thehydrogenated hydrocarbon tackifier is present in a range from about 5 toabout 90 percent by weight, based on the total weight of the pressuresensitive adhesive composition. In some embodiments, poly(cyclic olefin)is blended with about 10 to about 95 percent by weight polyisobutylene,based on the total weight of the pressure sensitive adhesivecomposition. In some embodiments, the pressure sensitive adhesivecomprises hydrogenated hydrocarbon (e.g., poly(cyclic olefin)) tackifierin a range from about 5 to about 70 weight percent, based on the totalweight of the pressure sensitive adhesive composition and about 30 toabout 95 weight percent polyisobutylene, based on the total weight ofthe pressure sensitive adhesive composition. In some embodiments, ahydrogenated hydrocarbon tackifier (in some embodiments, the poly(cyclicolefin)) is present in an amount of less than 20 (in some embodiments,less than 15) percent by weight, based on the total weight of thepressure sensitive adhesive composition. For example, the hydrogenatedhydrocarbon tackifier (in some embodiments, the poly(cyclic olefin)) maybe present in a range from 5 to 19.95, 5 to 19, 5 to 17, 5 to 15, 5 to13, or even 5 to 10 percent by weight, based on the total weight of thepressure sensitive adhesive composition. In some embodiments, thepressure sensitive adhesive is free of acrylic monomers andpolyacrylates. Exemplary polyisobutylene pressure sensitive adhesivesinclude adhesive compositions comprising a hydrogenated poly(cyclicolefin) and a polyisobutylene resin such as those reported in PCT Pub.No. WO 2007/087281 (Fujita et al.), the disclosure of which isincorporated herein by reference.

Exemplary hydrogenated hydrocarbon tackifiers for the optional fourthlayer are commercially available, for example, from Arakawa ChemicalIndustries Co., Ltd., Osaka, Japan, under the trade designations “ARKONP” and “ARKON M.” These materials are described in the trade literatureas being water white, hydrogenated hydrocarbon resins. Hydrogenatedhydrocarbon tackifiers under the trade designation “ARKON P” (e.g.,P-70, P-90, P-100, P-115, and P-140) are said to be fully hydrogenatedwhile those under the trade designation “ARKON M” (e.g., M-90, M-100,M-115, and M-135) are partially hydrogenated. The hydrogenatedhydrocarbon tackifier available under the trade designation “ARKONP-100” is said to have a number average molecular weight of about 850grams/mole, a softening point of about 100° C., and a glass transitiontemperature of about 45° C. The hydrogenated hydrocarbon tackifieravailable under the trade designation “ARKON P-140” has a number averagemolecular weight of about 1250 grams/mole, a softening point of about140° C., and a glass transition temperature of about 90° C. Thehydrogenated hydrocarbon tackifier available under the trade designation“ARKON M-90” has a number average molecular weight of about 730grams/mole, a softening point of about 90° C., and a glass transitiontemperature of about 36° C. The hydrogenated hydrocarbon tackifieravailable under the trade designation “ARKON-M-100” has a number averagemolecular weight of about 810 grams/mole, a softening point of about100° C., and a glass transition temperature of about 45° C.

Other exemplary hydrogenated hydrocarbon tackifiers for the optionalfourth layer are available, for example, from Exxon Chemical under thetrade designations “ESCOREZ 1315,” “ESCOREZ 1310LC,” “ESCOREZ 1304,”“ESCOREZ 5300,” “ESCOREZ 5320,” “ESCOREZ 5340,” “ESCOREZ 5380,” “ESCOREZ5400,” “ESCOREZ 5415,” “ESCOREZ 5600,” “ESCOREZ 5615,” “ESCOREZ 5637,”and “ESCOREZ 5690.”

The “1300” series resins are described in the trade literature as beingaliphatic resins with a high softening point. The “ESCOREZ 1315” resinis said to have a weight average molecular weight of about 2200grams/mole, a softening point in the range of about 112° C. to about118° C., and a glass transition temperature of about 60° C. The “ESCOREZ1310LC” resin is said to have a light color, a weight average molecularweight of about 1350 grams/mole, a softening point of about 95° C., anda glass transition temperature of about 45° C. The “ESCOREZ 1304” resinis said to have a weight average molecular weight of about 1650grams/mole, a softening point in the range of about 97° C. to about 103°C., and a glass transition temperature of about 50° C.

The “5300” series of resins are described in the trade literature asbeing water white, cycloaliphatic hydrocarbon resins, and have a weightaverage molecular weight in the range of about 370 grams/mole to about460 grams/mole, a softening point in the range of about 85° C. to about140° C., and a glass transition temperature in the range of about 35° C.to about 85° C.

The “5400” series of resins are described in the trade literature asbeing very light colored cycloaliphatic hydrocarbon resins, and have aweight average molecular weight in the range of about 400 grams/mole toabout 430 grams/mole, a softening point in the range of about 103° C. toabout 118° C., and a glass transition temperature in the range of about50° C. to about 65° C.

The “5600” series of resins are described in the trade literature asbeing very light colored, aromatic modified cycloaliphatic resin wherethe percent of aromatic hydrogen atoms is in the range of about 6 toabout 12 weight percent based on the weight of all the hydrogen atoms inthe resins. Further, the “5600” series of resins are said to have aweight average molecular weight in the range of about 480 grams/mole toabout 520 grams/mole, a softening point in the range of about 87° C. toabout 133° C., and a glass transition temperature in the range of about40° C. to about 78° C.

Other exemplary suitable hydrogenated hydrocarbon tackifiers for theoptional fourth layer are available, for example, from Eastman,Kingsport, Tenn., under the trade designations “REGALREZ 1085,”“REGALREZ 1094,” “REGALREZ 1126,” “REGALREZ 1139,” “REGALREZ 3102,” and“REGALREZ 6108.” These resins are described in the trade literature ashydrogenated aromatic pure monomer hydrocarbon resins. They have aweight average molecular weight ranging from about 850 grams/mole toabout 3100 grams/mole, a softening temperature in the range of about 87°C. to about 141° C., and a glass transition temperature in the range ofabout 34° C. to about 84° C. The “REGALEZ 1018” resin can be used inapplications that do not generate heat. This tackifying resin has aweight average molecular weight of about 350 grams/mole, a softeningpoint of about 19° C., and a glass transition temperature of about 22°C.

Other exemplary hydrogenated hydrocarbon tackifiers are available, forexample, from Cray Valley, Exton, Pa., under the trade designations“WINGTACK 95” and “WINGTACK RWT-7850.” The trade literature describesthese tackifying resins as synthetic resins obtained by cationicpolymerization of aliphatic C₅ monomers. The tackifying resin availableunder the trade designation “WINGTACK 95” is a light yellow solid with aweight average molecular weight of about 1700 grams/mole, a softeningpoint of 98° C., and a glass transition temperature of about 55° C. Thetackifying resin available under the trade designation “WINGTACKRWT-7850” is a light yellow solid with a weight average molecular weightof about 1700 grams/mole, a softening point of about 102° C., and aglass transition temperature of 52° C.

Other exemplary hydrogenated hydrocarbon tackifiers are available, forexample, from Eastman under the trade designations “PICCOTAC 6095-E,”“PICCOTAC 8090-E,” “PICCOTAC 8095,” “PICCOTAC 8595,” “PICCOTAC 9095,”and “PICCOTAC 9105.” The trade literature describes these resins asaromatic modified, aliphatic hydrocarbon resin or as aromatic modifiedC₅ resins. The tackifier available under the trade designation“PICCOTACK 6095-E” has a weight average molecular weight of about 1700grams/mole and a softening point of about 98° C. The tackifier availableunder the trade designation “PICCOTACK 8090-E” has a weight averagemolecular weight of about 1900 grams/mole and a softening point of about92° C. The tackifier available under the trade designation “PICCOTACK8095” has a weight average molecular weight of about 2200 grams/mole anda softening point of about 95° C. The tackifier available under thetrade designation “PICCOTAC 8595” has a weight average molecular weightof about 1700 grams/mole and a softening point of about 95° C. Thetackifier available under the trade designation “PICCOTAC 9095” has aweight average molecular weight of about 1900 grams/mole and a softeningpoint of about 94° C. The tackifier available under the tradedesignation “PICCOTAC 9105” has a weight average molecular weight ofabout 3200 grams/mole and a softening point of about 105° C.

In some embodiments, the hydrogenated hydrocarbon tackifier is ahydrogenated poly(cyclic olefin) polymer. Poly(cyclic olefin) polymersgenerally have low moisture permeability and can impact the adhesiveproperties of the polyisobutylene resin, for example, by functioning asa tackifier. Exemplary hydrogenated poly(cyclic olefin) polymers includehydrogenated petroleum resins; hydrogenated terpene-based resins (e.g.,available from Yasuhara Chemical, Hiroshima, Japan, under the tradedesignation “CLEARON,” in grades P, M, and K); hydrogenated resin orhydrogenated ester-based resins (available, for example, from HerculesInc., Wilmington, Del., under the trade designations “FORAL AX” and“FORAL 105” and from Arakawa Chemical Industries Co., Ltd., Osaka,Japan, under the trade designations “PENCEL A,” “ESTERGUM H,” and “SUPERESTER A”); disproportionate resins or disproportionate ester-basedresins (available, for example, from Arakawa Chemical Industries Co.,Ltd. under the trade designation “PINECRYSTAL”); a hydrogenateddicyclopentadiene-based resin (e.g., a hydrogenated C₅-type petroleumresin obtained by copolymerizing a C₅ fraction such as pentene,isoprene, or piperine with 1,3-pentadiene produced through thermaldecomposition of petroleum naphtha (available, for example, from ExxonChemical Co. under the trade designations “ESCOREZ 5300” and “ESCOREZ5400” and from Eastman Chemical Co. under the trade designation“EASTOTAC H”)); a partially hydrogenated aromatic modifieddicyclopentadiene-based resin (available, for example, from ExxonChemical Co. under the trade designation “ESCOREZ 5600”); a resinresulting from hydrogenation of a C₉-type petroleum resin obtained bycopolymerizing a C₉ fraction such as indene, vinyltoluene and α- orβ-methylstyrene produced by thermal decomposition of petroleum naphtha(available, for example, from Arakawa Chemical Industries Co., Ltd.under the trade designations “ARCON P” or “ARCON M”); and a resinresulting from hydrogenation of a copolymerized petroleum resin of theabove-described C₅ fraction and C₉ fraction available, for example, fromIdemitsu Petrochemical Co., Tokyo, Japan, under the trade designation“IMARV”). In some embodiments, the hydrogenated poly(cyclic olefin) is ahydrogenated poly(dicyclopentadiene), which may provide advantages tothe PSA (e.g., low moisture permeability and transparency).

The hydrogenated hydrocarbon tackifier generally has a solubilityparameter (SP value), which is an index for characterizing the polarityof a compound, that is similar to that of the polyisobutylene andexhibits good compatibility (i.e., miscibility) with the polyisobutyleneso that a transparent film can be formed. The tackifying resins aretypically amorphous and have a weight average molecular weight nogreater than 5000 grams/mole. If the weight average molecular weight isgreater than about 5000 grams/mole, compatibility with thepolyisobutylene material may decrease, tackiness may decrease, or both.The molecular weight is often no greater than 4000 (in some embodimentsno greater than 2500, 2000, 1500, 1000, or even no greater than 500; insome embodiments, the molecular weight is in the range of 200 to 5000,200 to 4000, 200 to 2000 or even 200 to 1000) grams/mole.

In some embodiments, polymeric multilayer films described herein furthercomprise at least one continuous (i.e., does not containing openingsextending from one major surface to another major surface) layer. Insome embodiments, a continuous layer adjacent to a layer exhibiting arandom network of strands and connective regions becomes textured fromthe random network of strands and connective regions (e.g., thecontinuous layer may conform at least in part to the texture of therandom network of strands and connective regions). Exemplary continuouslayers comprise at least one of a polyolefinic material (e.g.,polypropylene and/or polyethylene), modified polyolefinic material,polyvinyl chloride, polycarbonate, polystyrene, polyester (includingco-polyester), polylactide, polyvinylidene fluoride, (meth)acrylic(e.g., polymethyl methacrylate), urethane, acrylic urethane, ethylenevinyl acetate copolymer, acrylate-modified ethylene vinyl acetatepolymer, ethylene acrylic acid copolymers, nylon, engineering polymer(e.g., a polyketone and/or polymethylpentane), or elastomer (e.g.,natural rubber; synthetic rubber; styrene block copolymer containingisoprene, butadiene, or ethylene (butylene) blocks;metallocene-catalyzed polyolefin, polyurethanes; orpolydiorganosiloxane).

Continuous layers can be provided by techniques known in the art, suchas hot melt extrusion of an extrudable composition comprising thecomponents of the continuous layer composition. Exemplary methods formaking extrudable continuous layers are described, for example, inProgelhof, R. C., and Throne, J. L., “Polymer Engineering Principles,”Hanser/Gardner Publications, Inc., Cincinnati, Ohio, 1993, thedisclosure of which is incorporated herein by reference.

Alternatively, for example, at least one layer may be extruded as aseparate sheet and laminated together. In some embodiments, thesubstrate can advantageously combine the best properties of severalresins in the various layers while minimizing the use of the mostexpensive resins, leading to a higher value and lower cost imagereceptor medium. For example, the substrate layer may be made withresins of generality low cost that can be chosen to provide specificallydesired physical properties to the multilayered film. These propertiesmay include dimensional stability, tear resistance, conformability,elastomeric properties, die cuttability, stiffness, and heat resistance.

In some embodiments, a continuous layer is a skin layer. In someembodiments, at least one layer exhibiting a random network of strandsand connective regions is disposed between two continuous layers. Insome embodiments, a continuous layer is disposed between two layersexhibiting a random network of strands and connective regions.

In some embodiments, a first continuous layer is free of a pressuresensitive adhesive, and the layer exhibiting a random network of strandsand connective regions comprises a pressure sensitive adhesive. In someembodiments, a first continuous layer comprises a first pressuresensitive adhesive, and the layer exhibiting a random network of strandsand connective regions comprises a second pressure sensitive adhesive.

In some embodiments comprising more than one layer exhibiting a randomnetwork of strands and connective regions, at least two such layersexhibit different random network of strands and connective regions.

In some embodiments comprising more than one layer exhibiting a randomnetwork of strands and connective regions, one layer exhibiting a randomnetwork of strands and connective regions is free of a pressuresensitive adhesive, and another layer exhibiting a random network ofstrands and connective regions comprises a pressure sensitive adhesive.

In some embodiments comprising more than one layer exhibiting a randomnetwork of strands and connective regions, one layer exhibiting a randomnetwork of strands and connective regions comprises a first pressuresensitive adhesive, and another layer exhibiting a random network ofstrands and connective regions comprises a second, different pressuresensitive adhesive.

In some embodiments, a polymeric multilayer film described hereinfurther comprises a second continuous layer, wherein the first layerexhibiting a random network of strands and connective regions isdisposed between the first and second continuous layers.

In some embodiments, polymeric multilayer films described herein have athickness in a range from 1 micrometer to 1000 micrometers (in someembodiments, in a range from 25 micrometers to 500 micrometers, 50micrometers to 250 micrometers, or even 2 micrometers to 10micrometers).

In some embodiments, polymeric multilayer films described herein have amachine and cross-machine direction, wherein the polymeric multilayerfilm is elastic in the cross-machine direction.

In some embodiments, polymeric multilayer films described herein furthercomprise at least one liner. For example, a liner having a major surfaceattached to either the first or second major surface of the polymericmultilayer film. In some embodiments, each major surface of thepolymeric multilayer film has a liner attached thereto. In someembodiments, the liner comprises a polymeric multilayer film exhibitinga random network of strands and connective regions. In some embodiments,the liner has a major surface exhibiting a random network of strands andconnective regions. In some embodiments, the polymeric multilayer filmhas an adhesive (e.g., a pressure sensitive adhesive) layer on the majorsurface of the liner. For liners having a major surface exhibiting arandom network of strands and connective regions, the major surface ofthe adhesive on the major surface of the liner has the inverse surfaceof the major surface of the liner. In some embodiments, the first orsecond major surface of the polymeric multilayer film attached to themajor surface of the liner is an adhesive (e.g., a pressure sensitiveadhesive) surface. For liners having a major surface exhibiting a randomnetwork of strands and connective regions, the major surface of thepolymeric multilayer film attached to the liner has the inverse surfaceof the major surface of the liner.

Embodiments of polymeric multilayer films described herein are useful,for example, for tape and graphic articles (e.g., a graphic film). A“graphic film” is a film that absorbs at least some light havingwavelengths in the visible or near infrared range and reflects at leastsome light in the visible range where the reflected light contains somegraphical content. The graphical content may include patterns, images orother visual indicia. The graphic film may be a printed film or thegraphic may be created by means other than printing. For example, thegraphic film may be perforated reflective film with a patternedarrangement of perforations. The graphic may also be created byembossing. In some embodiments, the graphic film is a partiallytransmissive graphic film (e.g., in use in a backlighted sign (e.g., abacklighted traffic sign)). Advertising and promotional displays ofteninclude graphic images appearing on structural surfaces such as trucksides and awnings, or free-hanging as banners. To prepare the display,an image may be formed on an adhesive-backed image receptor medium,sometimes referred to as a graphic marking film, which is then adheredto the desired substrate. Although the graphic display may be intendedfor a long-term installation of 5 years or more, it is often arelatively short term (3 months to 1 year) outdoor installation. In thecase of a short-term display, the image receptor medium is desirably alow cost, weather resistant, durable graphic marking film having goodprintability and adhesion of inks and/or toners that is easily appliedto and removed from a surface.

Exemplary Embodiments

-   1. A polymeric multilayer film comprising at least two adjacent    polymeric layers each exhibiting a random network of strands (in    some embodiments, elongated strands) and connective regions (the    random network has a first optical density and the connective    regions has a second optical density, wherein the first optical    density is greater than the second optical density; in some    embodiments, there are openings in at least some of the connective    regions, whereas in some embodiments there are no openings (i.e., no    through holes) in the layer). In some embodiments, at least 3, 4, 5,    6, or even at least 7 polymeric layers, each exhibiting a random    network of strands and connective regions. In some embodiments, one    or more additional polymeric layers exhibiting a random network of    strands and connective regions comprise a pressure sensitive    adhesive, each of which may be the same or different from the first    pressure sensitive adhesive or from each other.-   2. The polymeric multilayer film of Exemplary Embodiment 1, wherein    the layers exhibiting a random network of strands and connective    regions independently comprise at least one of a polyolefinic    material (e.g., polypropylene and/or polyethylene), modified    polyolefinic material, polyvinyl chloride, polycarbonate,    polystyrene, polyester (including co-polyester), polylactide,    polyvinylidene fluoride, (meth)acrylic (e.g., polymethyl    methacrylate), urethane, acrylic urethane, ethylene vinyl acetate    copolymer, acrylate-modified ethylene vinyl acetate polymer,    ethylene acrylic acid copolymers, nylon, engineering polymer (e.g.,    a polyketone and/or polymethylpentane), or elastomer (e.g., natural    rubber; synthetic rubber; styrene block copolymer containing    isoprene, butadiene, or ethylene (butylene) blocks;    metallocene-catalyzed polyolefin, polyurethanes; or    polydiorganosiloxane).-   3. The polymeric multilayer film of any preceding Exemplary    Embodiment, wherein at least one layer exhibiting a random network    of strands and connective regions has an open porosity of at least 1    (in some embodiments, at least 5, 10, 15, 20, 25, 30, 35, 40, 45,    50, 55, 60, 65, 70, 75, or even at least 80; in some embodiments, in    a range from 1 to 80) percent.-   4. The polymeric multilayer film of any preceding Exemplary    Embodiment, wherein at least one layer exhibiting a random network    of strands and connective regions is separable from the remaining    polymeric multilayer film.-   5. The polymeric multilayer film of Exemplary Embodiment 4, wherein    the layer exhibiting a random network of strands and connective    regions is essentially free of pressure sensitive adhesive.-   6. The polymeric multilayer film of Exemplary Embodiment 4, wherein    the layer exhibiting a random network of strands and connective    regions comprises a pressure sensitive adhesive.-   7. The polymeric multilayer film of any preceding Exemplary    Embodiment further comprising a first continuous layer.-   8. The polymeric multilayer film of Exemplary Embodiment 7, wherein    the first continuous layer is free of a pressure sensitive adhesive,    and wherein the layer exhibiting a random network of strands and    connective regions comprises a pressure sensitive adhesive.-   9. The polymeric multilayer film of Exemplary Embodiment 7, wherein    the first continuous layer comprises a first pressure sensitive    adhesive, and wherein the layer exhibiting a random network of    strands and connective regions comprises a second pressure sensitive    adhesive.-   10. The polymeric multilayer film of Exemplary Embodiment 9, wherein    the first pressure sensitive adhesive has more tack than the second    pressure sensitive adhesive.-   11. The polymeric multilayer film of Exemplary Embodiment 7, wherein    the first pressure sensitive adhesive has less tack than the second    pressure sensitive adhesive.-   12. The polymeric multilayer film of Exemplary Embodiment 7, wherein    the first continuous layer comprise at least one of a polyolefinic    material (e.g., polypropylene and/or polyethylene), modified    polyolefinic material, polyvinyl chloride, polycarbonate,    polystyrene, polyester (including co-polyester), polylactide,    polyvinylidene fluoride, (meth)acrylic (e.g., polymethyl    methacrylate), urethane, acrylic urethane, ethylene vinyl acetate    copolymer, acrylate-modified ethylene vinyl acetate polymer,    ethylene acrylic acid copolymers, nylon, engineering polymer (e.g.,    a polyketone and/or polymethylpentane), or elastomer (e.g., natural    rubber; synthetic rubber; styrene block copolymer containing    isoprene, butadiene, or ethylene (butylene) blocks;    metallocene-catalyzed polyolefin, polyurethanes; or    polydiorganosiloxane).-   13. The polymeric multilayer film of either Exemplary Embodiment 7    or 12, wherein the first continuous layer is a skin layer.-   14. The polymeric multilayer film of any of Exemplary Embodiments 7,    12, or 13, further comprising a second layer exhibiting a random    network of strands and connective regions.-   15. The polymeric multilayer film of Exemplary Embodiment 14,    wherein the second layer exhibiting a random network of strands and    connective regions has a different random network of strands and    connective regions than the first layer comprising a random network    of strands and connective regions.-   16. The polymeric multilayer film of Exemplary Embodiment 15,    wherein the first layer exhibiting a random network of strands and    connective regions is free of a pressure sensitive adhesive, and    wherein the second layer exhibiting a random network of strands and    connective regions comprises a pressure sensitive adhesive.-   17. The polymeric multilayer film of Exemplary Embodiment 15,    wherein the first layer exhibiting a random network of strands and    connective regions comprises a first pressure sensitive adhesive,    and wherein the second layer exhibiting a random network of strands    and connective regions comprises a second, different pressure    sensitive adhesive.-   18. The polymeric multilayer film of Exemplary Embodiment 15,    wherein the first pressure sensitive adhesive has more tack than the    second pressure sensitive adhesive.-   19. The polymeric multilayer film of any of Exemplary Embodiments 14    to 18, wherein the first continuous layer is disposed between the    first and second layers exhibiting a random network of strands and    connective regions.-   20. The polymeric multilayer film of any of Exemplary Embodiments 7    to 18, further comprising a second continuous layer, wherein the    first layer exhibiting a random network of strands and connective    regions is disposed between the first and second continuous layers.-   21. The polymeric multilayer film of any preceding Exemplary    Embodiment, wherein at least one of the first or second (in some    embodiments each of the first and second) major surfaces of the    polymeric multilayer film exhibits a random network of strands and    connective regions.-   22. The polymeric multilayer film of any preceding Exemplary    Embodiment having a thickness in a range from 1 micrometer to 1000    micrometers (in some embodiments, in a range from 25 micrometers to    500 micrometers, 50 micrometers to 250 micrometers, or even 2    micrometers to 10 micrometers).-   23. The polymeric multilayer film of any preceding Exemplary    Embodiment, further comprising at least one of a die or pigment    (e.g., imparting a color such as white, yellow, green, blue, red,    orange, brown, black, etc.).-   24. The polymeric multilayer film of any preceding Exemplary    Embodiment, further comprising at least one antistatic material.-   25. The polymeric multilayer film of any preceding Exemplary    Embodiment, further comprising at least one of an ink or paint    receptive material.-   26. The polymeric multilayer film of any preceding Exemplary    Embodiment, further comprising metallic (e.g., aluminum, bronze,    stainless steel, zinc, iron, tin, silver, gold, and/or titanium)    particles.-   27. The polymeric multilayer film of any preceding Exemplary    Embodiment, further comprising a release agent.-   28. The polymeric multilayer film of any preceding Exemplary    Embodiment, further comprising an abrasion resistant material.-   29. The polymeric multilayer film of any preceding Exemplary    Embodiment, further comprising at least one of a slip or antiblock    agent.-   30. The polymeric multilayer film of any preceding Exemplary    Embodiment, further comprising a hinder amine light stabilizer    (HALS).-   31. The polymeric multilayer film of any preceding Exemplary    Embodiment, further comprising an UV stabilizer.-   32. The polymeric multilayer film of any preceding Exemplary    Embodiment, further comprising a hydrophilic material.-   33. The polymeric multilayer film of any preceding Exemplary    Embodiment having a machine and cross-machine direction, wherein the    polymeric multilayer film is elastic in the cross-machine direction.-   34. The polymeric multilayer film of any preceding Exemplary    Embodiment, further comprising a liner having a major surface    attached to either the first or second major surface of the    polymeric multilayer film. In some embodiments, each major surface    of the polymeric multilayer film has a liner attached thereto.-   35. The polymeric multilayer film of Exemplary Embodiment 34,    wherein the liner comprises a polymeric multilayer film exhibiting a    random network of strands and connective regions.-   36. The polymeric multilayer film of either Exemplary Embodiment 34    or 35, wherein the liner has a major surface exhibiting a random    network of strands and connective regions.-   37. The polymeric multilayer film of any of Exemplary Embodiments 34    to 36 having an adhesive (e.g., a pressure sensitive adhesive) layer    on the major surface of the liner. For liners having a major surface    exhibiting a random network of strands and connective regions, the    major surface of the adhesive on the major surface of the liner has    the inverse surface of the major surface of the liner.-   38. The polymeric multilayer film of any of Exemplary Embodiments 34    to 36, wherein the first or second major surface of the polymeric    multilayer film attached to the major surface of the liner is an    adhesive (e.g., a pressure sensitive adhesive) surface. For liners    having a major surface exhibiting a random network of strands and    connective regions, the major surface of the polymeric multilayer    film attached to the liner has the inverse surface of the major    surface of the liner.-   39. A graphic article comprising the polymeric multilayer film of    any preceding of Exemplary Embodiment.-   40. A tape (e.g., duct tape) comprising the polymeric multilayer    film of any of Exemplary Embodiments 1 to 38.

Advantages and embodiments of this invention are further illustrated bythe following examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this invention. All parts andpercentages are by weight unless otherwise indicated.

EXAMPLE 1

A seven-layer film was produced using a seven-layer annular stack die(obtained under the trade designation “COEX 7-LAYER” (Type LF-400) fromLabtech Engineering, Samut Prakan, Thailand) using an apparatus as shownin FIGS. 3 and 3A, except there were only seven stacked die plates.Airflow to the die was manually controlled to achieve a blow-up ratio ofabout 2:1. The bubble was subsequently collapsed about 3 meters (10feet) above the die and rolled up. The feed materials were supplied by 7independent 20 mm diameter extruders with about a 30:1 length todiameter ratio.

A first extruder was used to melt and extrude a low-density polyethylene(obtained under the trade designation “PETROTHENE NA217000 5.6 MFI” fromLyondellBasell, Houston, Tex.) into an inside channel of the annularstack die. The melt temperature was maintained at 180° C. The second,third, fourth, and fifth extruders were used to feed the same resin insubsequent outer layers of the first resin. A sixth extruder was used tofeed a blend containing 96% of the same polyethylene with 4% of achemical blowing agent (obtained under the trade designation “ECOCELL H”from Polyfil Corp., Rockaway, N.J.). A melt temperature of 215° C. wasmaintained in layer 6. A seventh extruder was used to feed an identicalblend as the sixth extruder to the outside layer of the annular stackdie with a melt temperature of 180° C. A screw speed of 30 revolutionsper minute was used. The die temperature was maintained at 180° C.

An image of the resulting polymeric multilayer film is shown in FIGS. 4and 4A (see random network of strands 403 and connective regions 404).

EXAMPLE 2

A polymeric multilayer film was prepared as described in Example 1,except the first and second extruders contained only low-densitypolyethylene and the remaining extruders contained the described blendof chemical blowing agent and low-density polyethylene. For all layerscontaining a chemical blowing agent, a melt temperature of 215° C. wasmaintained. The die temperature was maintained at 180° C.

Images of the resulting polymeric multilayer film are shown in FIGS. 5and 5A (see random network of strands 503 and connective regions 504).

EXAMPLE 3

A polymeric multilayer film was prepared as described in Example 1,except a pressure sensitive adhesive (obtained under the tradedesignation “KRATON MD6748” (4.8 MFI) from PolyOne, Avon Lake, Ohio) wasused to blend with the chemical blowing agent.

Images of the resulting polymeric multilayer film are shown in FIGS. 6and 6A (see random network of strands 603 and connective regions 604).

Foreseeable modifications and alterations of this disclosure will beapparent to those skilled in the art without departing from the scopeand spirit of this invention. This invention should not be restricted tothe embodiments that are set forth in this application for illustrativepurposes.

What is claimed is:
 1. A polymeric multilayer film comprising at leasttwo adjacent blown polymeric film layers, wherein at least some of theblown polymeric film layers comprise a random network of strands andconnective regions, wherein the random network of strands has a firstoptical density and the connective regions have a second opticaldensity, and wherein the first optical density is greater than thesecond optical density.
 2. The polymeric multilayer film of claim 1,wherein at least one blown polymeric film layer has an open porosity ofat least 20 percent.
 3. The polymeric multilayer film of claim 1,wherein at least one blown polymeric film layer is separable from theremaining polymeric multilayer film.
 4. The polymeric multilayer film ofclaim 1, further comprising a continuous layer, wherein the continuouslayer is free of openings extending from a first major surface thereofto a second major surface thereof.
 5. The polymeric multilayer film ofclaim 4, wherein the continuous layer is free of a pressure sensitiveadhesive, and wherein at least one blown polymeric film layer comprisesa pressure sensitive adhesive.
 6. The polymeric multilayer film of claim5, wherein the continuous layer comprises a first pressure sensitiveadhesive, and wherein at least one blown polymeric film layer comprisesa second pressure sensitive adhesive different from the first pressuresensitive adhesive.
 7. The polymeric multilayer film of claim 6, whereinthe continuous layer is a skin layer.
 8. The polymeric multilayer filmof claim 1, wherein at least one of the first or second major surfacesof the polymeric multilayer film comprises a random network of strandsand connective regions.
 9. The polymeric multilayer film of claim 8,further comprising a liner having a major surface attached to either thefirst or second major surface of the polymeric multilayer film.
 10. Thepolymeric multilayer film of claim 9, wherein the liner has a majorsurface exhibiting a random network of strands and connective regions.11. The polymeric multilayer film of claim 1 having a machine andcross-machine direction, wherein the polymeric multilayer film iselastic in the cross-machine direction.
 12. A graphic article comprisingthe polymeric multilayer film claim
 1. 13. A tape comprising thepolymeric multilayer film of claim 1.